1. Field of the Invention
The present invention relates to flat panel flight instrument displays for use in aircraft.
2. Description of the Related Art
It is essential in the creation of graphical primary flight instruments for an aircraft that are to be used and relied upon by the flight crew that they be of ultra high reliability and integrity.
Currently, the Pilot Flight Display (PFD), Navigation Display (ND) and Engine/Electrical Display (ICAS) systems of an aircraft receive sensor data/inputs on all relevant parametersxe2x80x94about 100 pieces of data, the majority in the standard ARINC 429 serial format. This data is input to an image rendering Symbol Generator and is checked for reasonableness and validity. The parameters are then appropriately scaled to useable formats, and the commands to create various informational alphanumeric and graphical images for reporting the relevant data on a display screen viewable by the flight crew are executed using the scaled parameters; these commands include graphical primitives such as points and lines, pointer, arc, polygon and fill commands, and alphanumeric characters. A typical display is produced by thousands of such commands that are executed on the order of 100 times every second. Each of these generated graphical primitives or primitive command elements must then be rotated, translated and their color (e.g., red, blue, green) modified or changed or varied in response to the data signal values received by the Symbol Generator. The creation, orienting and positioning of these graphical features for imaging on a screen display require thousands, and commonly tens or hundreds of thousands, of lines of computer code. Once oriented and positioned, each primitive element is then rendered by calculating individual display field textels (points) and placing them into an 8 million byte pixel map in the video RAM, which is refreshed on the order of 100 times per second. The data fed to the graphical display screen must also be anti-aliased to smooth the generated image lines and thereby present to the flight crew a display that is both easy to read and interpret and which rapidly conveys the information that it is intended to represent. Anti-aliasing of display data, however, is extremely computationally intensivexe2x80x94typically 800 billion instructions/secondxe2x80x94since it is necessary to compute the locus of points along each line, arc, etc. and the intensity levels of the adjacent pixels (i.e those pixels adjacent to the computed data points) for smoothing of the graphical lines and images to be displayed. To avoid this high computational overhead many such displays use principally-vertical scales which do not require anti-aliasing of the image lines but which limit the ability of graphically-generated flight instruments to either graphically-depict (i.e. mimic) the conventional mechanical instruments with which the flight crew is familiar or present the flight instrument data in other convenient, legible, easily-utilized and readily-understandable formats.
The rapidly evolving computer processing and graphics display generation technology from the PC industry provides low cost and exceptionally powerful computing engines, both in CPUs like the Intel Pentium 4 and in special purpose 256-bit parallel rendering engines and the like from a multiplicity of companies. The availability of increasingly more powerful computing engines facilitates the implementation of ever more capable and complex display systems, since these new systems are capable of executing many more instructions (i.e. lines of code) per second. However, the size of this code and the complexity of the displays, especially in these new large formats, raises in the avionics industry the problem of having to test all code intended for use on an aircraft to the exacting standards required by the FAA (Federal Aviation Administration) for flight critical airborne equipment in order to certify the new and improved processor and display subsystems for permitted use on aircraft. The hundreds of thousands of instructions that are executed by such equipment to format and display the critical flight data are required by the FAA to undergo exhaustive, carefully-documented testing that commonly takes 5000 man-months for even relatively modest changes to previously-certified systems. Moreover, the low-cost, high performance hardware that is widely available to the public from the PC industry cannot currently be used in conventional aircraft instrumentation systems, because the design history and verification data for such hardware is not available from the manufacturer, and sufficient support data and testing has not been or will not be done by the manufacturer to demonstrate its operational reliability and design integrity.
Current aircraft instrumentation displays use typically dedicated processors and graphics rendering chips that have been specially designed for the particular application. FAA certification is based on a determination that both the hardware and the software of the display system have been thoroughly demonstrated, e.g. through extensive testing and documentation, to be operable in the intended aircraft flight deck environment and with the anticipated flight and environmental data without introducing unexpected errors or inaccuracies. Today, this generally requires that the history or heritage of the processor or chip design must be fully documented to the FAA and that the hardware and software must be tested by validating data flow through every pathway in the chip using the entire range of dataxe2x80x94i.e. every single valuexe2x80x94that the chip would be expected to handle during normal use on the aircraft. This process requires many, many months of testing. As a result, a manufacturer that wishes to periodically improve, for example, the graphics processor of an aircraft image rendering computer would spend virtually all of its time testing the new or improved chips. Despite the fact that current, widely-available, relatively inexpensive, off-the-shelf graphics processor chips are improved and become significantly more powerful and capable every 6 months or so, the specialty aircraft instrumentation processor chips and software used in these specialized aircraft displays are for practical reasons very infrequently updated or changed to thereby avoid the constant re-testing for re-certification that the FAA would require to adequately demonstrate the validity and integrity of the display data that they output.
Accordingly, there exists a need for an improved graphics display system for use in an aircraft and which can accommodate readily-upgradeable graphics display components and subsystems without adversely affecting existing FAA certification or requiring extensive recertification of the instrumentation display system.
An improvement over prior art aircraft instrumentation flight display systems and arrangements is provided by the present invention wherein a comparator processor is used in conjunction with a graphics rendering computer processor. The graphics rendering processorxe2x80x94from which the display presented to the flight crew is generatedxe2x80x94is operative for generating, from data provided by a bank of sensors and other environmental and operating parameters and aircraft inputs, the various commands needed for rendering anti-aliased graphically-presented data images on a display screen and, as such, is implemented by a relatively complex apparatus and data processing engine. In accordance with the invention, a separate comparator processor is provided for independently calculating at least a selected plurality of data point display locations and values from the same sensors and input data from which the rendering processor generates the images that are to be displayed to the flight crew. The comparator processor then compares its calculated select data point values and locations to the corresponding data points that have been generated for display by the graphics rendering processor to determine whether such values and locations are the same and thereby test the reliability of the rendering processor generated graphical image for display. If the corresponding data does not successfully compare, then an error condition is determined to exist and, if the error condition remains after several comparator calculation or display refresh cycles or other predetermined interval, an error indication is displayed on the graphical display screen. Since the comparator processor output data is intentionally insufficient for providing a complete rendered screen display but, rather, is utilized only as an integrity check on the data produced by the graphics rendering computer, no anti-aliasing functionality is required of the comparator processor. This, coupled with the preferred and intended operation of the comparator to calculate only the limited number of select data points used in the comparison, permits the use of a notably simplified comparator processor that requires far less processing power and fewer executable commands to provide its data processing and comparison functions than does the graphics rendering processor by which the image for display is generated. As a result, expeditious FAA certification of the comparator is attainable. The use of a comparator processor as a check on the integrity of the graphics rendering processor data also permits the ready substitution of upgraded rendering engine graphics processors as such components and systems become available without extensive, if any, subsequent testing and documentation to obtain FAA recertification since the associated comparator processor will generally remain unchanged.
In a preferred embodiment, duplicate flat panel display systems, each correspondingly constructed and operating in accordance with the invention, are mounted in an aircraft cockpit for independently supplying graphical data representations to a pilot and a co-pilot and/or other members of the flight crew, each of whom is thereby provided with a separate and independently-addressed display screen. In the event that an error in the rendering processor data is detected as a result of the comparison of that data with the select data points generated by the comparator processor of one of those display systems, the other display system can thereafter provide graphical imaging data to both the pilot and co-pilot display screens to thereby replace the data determined to be in error or, if necessary, to replace a larger portion of or the entire display screen field.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.